1. Field of the Invention
This invention relates to medical devices and in particular to apparatus for selectively measuring central venous pressure and effecting hyperalimentation of a patient.
2. Description of the Prior Art
In connection with patients requiring administration of parenteral fluids, it is often highly desirable to obtain a measurement of the central venous pressure of the patient so as to advise the clinician as to the fluid and blood status. The central venous pressure provides an indication of the fluid pressure at the right side of the heart. Examples of such patients include those who have undergone major trauma, major operations, septic patients, or patients who have possibility of fluid shifts. In such patients, it is important to continuously provide information as to the central venous pressure to the clinician.
Normally, the central venous pressure is measured by inserting a catheter through a peripheral vein into the right heart portion, or superior vena cava. A problem arises, however, in the conventional technique for effecting such central venous pressure measurement in that the techniques require the opening of a column of fluid to the atmosphere which destroys the complete sterility thereof.
Another problem in the conventional techniques for measuring central venous pressure is that in the techniques wherein the pressure is determined by a fluid manometer sensor, blood in the sensor may reflux and return through the connection to the patient, again providing a possibility of contamination.
It is common to utilize such central venous pressure determinations in connection with parenteral fluid administration. Illustratively, such sensing is utilized in connection with hyperalimentation, i.e. total parenteral nutrition, fluid administration. In such administration, large amounts of calories and proteins may be given to a patient so as to provide all necessary nutrients for growth, survival and healing. Such parenteral fluid administration is conventionally effected by means of a catheter placement similar to that used in the central venous pressure determinations. However, in connection with such parenteral fluid administration, the problem of sterility is of maximum importance as normally relatively high concentrations of glucose are utilized in such parenteral fluid administrations. Such high levels of glucose provide an ideal medium for bacterial growth and, thus, aggravate the sterility problem.
It is further desirable in such medical treatment to minimize the number of catheter insertions. Still further, it is desirable to effect the central venous pressure determinations concurrently with the administration of the parenteral fluids for optimum surveillance of the patient's conditions. Conventionally, two separate catheters have been employed from two separate sites in the superior vena cava vein to provide such concurrent pressure determination and parenteral fluid administration.
It is well known that insertion of such catheters has a morbidity factor of between approximately 0.2% to 0.5%. Further, the requirement of multiple catheter insertions limits the available venous access site.
A number of prior art patents have been directed to the use of manometers and parenteral fluid administration techniques. Illustratively, U.S. Pat. No. 3,242,920 of H. W. Andersen shows a manometer for measuring venous pressure and including an intravenous infusion supply connected to the manometer tube through a "T" connector.
Paul E. Rockwell, in U.S. Pat. No. 3,413,970 shows means for measuring central venous pressure utilizing a manometer with the manometer and a parenteral fluid supply being connected to the catheter inserted into the patient through a three-way valve.
In U.S. Pat. No. 3,590,818, Gerald T. Lemole shows a device having correlated manometer and intravenous fluid supply means wherein a three-way stopcock separately and at various times places the intravenous fluid against the manometer fluid, the intravenous fluid from the patient's veins against the manometer fluid, and provides intravenous fluid from the source to the vein.
Saul Leibinsohn, in U.S. Pat. No. 3,690,312, shows a venous pressure manometric device with level magnifying means wherein a stopcock interconnects a plurality of the fluid carrying ducts of the system. In taking the venous pressure with the Leibinsohn device, sterile isosmotic water is allowed to run into the reservoir tube by suitable positioning of the stopcock rotatable plug. Subsequently, the plug is again rotated to allow the water to flow by gravity into the patient. A bag is secured to the upper end of the manometer tube for expansively closing the tube.
Curt Danielsson, in U.S. Pat. No. 3,934,576, shows a system including a multiway valve for selectively connecting pressure measuring means and fluid supply means to the catheter inserted into the patient. The catheter may comprise a valved catheter. Luer-Lok connecting means may be utilized at different portions of the system.